Crocheted Rings

I've been thinking about making crocheted rings.  I have one of those really big cocktail rings and I thought I could make one out of yarn.

My idea is to make rosettes out of scraps of yarn and then attach them to rings made out of stretchable string.  I'm making a bunch of rosettes first, using Lion Brand's Crocheted Rosettes/Flowers pattern.  I'm pretty sure I have stretchy string around somewhere and really hope I don't have to buy more.